1. Field of the Invention
This invention relates to an inflatable seal for sealing the annulus between an outer hollow member and an inner member contained therein, and more particularly, but not by way of limitation, relates to an inflatable grouting seal to support a column of grout while the grout is setting in the annulus between the jacket leg of an offshore platform and a pile driven therethrough.
2. Description of the Prior Art
Offshore platforms are usually fabricated either in a harbor or at an onshore location, and are subsequently transported on barges or towed horizontally through the water to a marine site where they are uprighted and lowered so that the legs of the platforms rest on the ocean floor. The offshore platform legs are hollow structures having pilings driven downwardly therethrough into subterranean formations below the ocean floor to anchor the platform in position. These pilings are typically welded to the jacket legs of the platform near the top of the platform. Additionally, in many instances it is desirable to fill the annulus between the jacket leg and the piling with grouting material so that a unitary load-bearing structure is created. To facilitate the grouting of the annulus between the jacket leg and the piling a grout seal or grout packer is frequently utilized.
A typical prior art packer which has been utilized by the assignee of the present invention is that shown in U.S. Pat. No. 4,337,010 to Sullaway et al. The Sullaway packer has an inflatable packer element which is bonded to end rings which are in turn sealingly welded to the inner bore of a housing member. As seen in FIG. 3 of Sullaway, the packer is inflated by pumping pressurized fluid into the space between the inner bore of the housing and the outer surface of the packer element. The Sullaway packer relies upon the weld seal between the end rings and the housing to contain this pressurized fluid. In order to test the packer of Sullaway, prior to actual use on an offshore platform, it is necessary for the inflatable packer element and its end rings to be installed in its housing and welded in place. Subsequently the entire housing must be welded in place as a portion of the jacket leg of an offshore platform. This is an inconvenience in that many customers prefer to provide their own outer housing element and to utilize a packer which can be tested prior to being installed in the housing element.
Another design of grout packer which is in common usage is that shown in U.S. Pat. No. 3,468,132 to Harris. The Harris packer utilizes an inflatable bladder having radially inner and outer walls with an inflation cavity defined therebetween. The inflation fluid is pumped into the inflation cavity to expand the bladder. The axial ends of the bladder are mechanically but not sealingly connected to end rings which are received within the outer housing. If the bladder of Harris leaks, the packer will fail.